Q: Kleenex と tissue はどう違いますか?
A: @sidney: Tissue is the more commonly used term.
Q: Kleenex と Tissue paper はどう違いますか?
A: Some people do say Kleenex instead of tissue paper because Kleenex is a very popular tissue paper brand. Although many people do say tissue, but not with paper on the end. For example, "I need a tissue." If you say "tissue paper", that's more of a crafting paper. So basically:
Kleenex = tissue (are the same thing)

Tissue paper = a thin paper used for crafts

Hope that helped out :)


Q: This Kleenex was very cheap. I got it on a sale yesterday. この表現は自然ですか?
A: "I got it/them on sale yesterday" sounds more natural! :)
Q: Kleenex gets gone soon in my family. この表現は自然ですか?
A: ”Kleenx quickly disappear in my family" is how I would say it.
Q: Who used this Kleenex and didn't throw away? Throw it away. この表現は自然ですか?
A: "didn't throw it away"

Put an "it" in there
Q: Can I have a Kleenex?
ティッシュ一枚もらってもいい? この表現は自然ですか?
A: "Can I have a tissue?" Also works.
Q: Kleenex runs out quickly these days in this room. この表現は自然ですか?
A: It's really only a matter of taste, but "these days in this room" clashes a bit. You could rearrange it into "nowadays the kleenex in this room runs out quickly" or "kleenex in this room runs out quickly these days".